Perovskite solar cell, methods and uses thereof

Abstract

The present disclosure relates a process for immobilization of soluble lead compounds in perovskite solar cells in the case of the cell breakage or of fire, by introducing the additives in the cells. The additives, upon contact with water,interact with lead-based components of the perovskite cell via ion-exchange reaction forming less soluble compounds with higher thermal stability. The less soluble lead compounds formed in the disclosed method reduce by two orders of magnitude the release of lead ions from perovskite cell if it leaks. Another aspect of the disclosure is described as an additive in the perovskite cell of a water absorber made from hydrophilic polymer; it swallows the water, expands inside the cell blocking the water path through cracks in the cell. The release of lead from the perovskite solar cell with the disclosed additives was reduced by four orders of magnitude compared to a blank cell.

Description

DESCRIPTIONPEROVSKITE SOLAR CELL, METHODS AND USES THEREOFTechnical field

[0001] The present disclosure relates to a perovskite solar cell with an additive for lead immobilization and to a process for immobilizing soluble lead compounds within these cells to mitigate lead release in the event of cell breakage or fire by introducing specific additives.Background art

[0002] Converting solar energy into electricity through thin film photovoltaic technologies is being a challenge for the scientific community for the last two decades.

[0003] Perovskite solar cells are one of the most intensively investigated and promising photovoltaic technologies to date, allowing to reach the efficiency of solar light to electrical power conversion above 25% [1],

[0004] A typical perovskite solar cell comprises a photoelectrode and a counter electrode with a perovskite light absorbing layer located between them.

[0005] The general chemical formula of perovskite light absorber is expressed as ABX3 wherein A represents at least one of alkali metal ions, methylamine ions, ethylamine ions, NHzCH=NH2 ions or alkylamine ions, B represents at least one of the group IV element (Ge, Sn, Pb), the group III indium (In) and the group V antimony (Sb), and X represents at least one of the elements of the group VII (F, Cl, Br, l)[2],

[0006] The most efficient perovskite solar cells utilize lead (Pb) halide perovskites in the light absorbing layer [3] which, however, vigorously decompose when exposed to the humid atmosphere:CH3NH3PbX3+ O2= CH3NH2+ PbX2+ 1 / 2H2O + 1 / 2X2, wherein X = I, Br or Cl (eq.l)

[0007] The decomposition (eq.l) is almost instantaneous in direct contact of the perovskite with water. The lead halides formed (eq.l) are quite soluble in water: 0.76 g-L-1, 8.7 g-L1and 9.8 g-L1at 20°C for Pbh, PbBr2 and PbCl2, respectively.

[0008] Lead and its soluble compounds are highly poisonous, affecting almost every organ and system in the human body. In 1992 the World Health Organization established 10 pg-L1as the maximum acceptable concentration of lead in drinking water.

[0009] The amount of water-soluble lead compounds in a conventional perovskite solar cell is ca. 14 pg-cm-2to 30 pg-cm-2. This means that a perovskite solar cell panel with an area of 1 m2contain ca. 140 mg to 300 mg of lead and may contaminate with lead ca. 14-30 m3of water up to the lead level threatening human health.

[0010] The content of soluble lead compounds in perovskite solar cells is of great concern and may compromise the future of the perovskite solar cell. Perovskite solar cells should be hermetically packed, not only to keep them stable for long-term conditions but also to prevent possible lead leakages from the cells.

[0011] During outdoor operation, the perovskite solar cells are exposed to various aggressive factors such as intensive sunlight, daily and seasonal cycles of temperatures, precipitations and wind gusts. Additionally, mechanical stress and / or mechanical impacts may open small or big cracks in the cell package, while fire could have a more destructive action.

[0012] Breakage of the package tightness allows the toxic lead to leak if humidity and water enter the cell.

[0013] There is then the need for a reliable immobilization process of lead in lead-containing perovskite solar cells, to efficiently minimize and preferably to prevent possible releases of lead pollutants from the perovskite solar cells in case of losing the cell hermicity.

[0014] Jiang, Y. et al., in Reduction of lead leakage from damaged lead halide perovskite solar modules using self-healing polymer-based encapsulation for Nature Energy, reported the procedure for reduction of lead leakage from damaged lead halide perovskite solar cell modules. The reduction of lead leakage from the damaged perovskite solar cells was achieved by using epoxy resin with a self-healing ability as a sealing material for encapsulation of the cell. The present disclosure differs from the reported procedure in the way that a new additive is added to the cell. The disclosed element is a salt that chemically reacts with soluble lead species constituting the perovskite light absorber forming insoluble lead compounds or lead compounds with very low solubility in water.

[0015] Document EP 0190896 A describes a method for lead ion removal from solution via ionexchange reaction. It is characterized in that water-insoluble calcium and strontium salts are used to remove lead ions from the solution.

[0016] Additionally, document US 6106725 describes a method of removing lead ions from drinking water using an ion-exchange reaction and consists of directing the water flow through a matrix comprising phosphate mineral with a very phosphate with low solubility in water, and a solid carbonate mineral which is slightly soluble in water. The present disclosure also uses an ionexchange reaction to reduce the concentration of lead ions in water leaking from the damaged perovskite solar cell but differs from the above documents in that the water-soluble salts are used for the ion-exchange reaction to capture the lead ions. This allows achieving a much higher concentration of the anion, that constitutes an insoluble salt of lead, thereby reducing the equilibrium concentration of dissolved lead in the solution more efficiently.

[0017] Perovskite solar cells are a promising technology in photovoltaic energy conversion due to their high efficiency and low manufacturing costs. However, the lead content in these cells poses environmental and health risks ifthe cells breakor are exposed to fire, potentially releasing soluble lead compounds. There is a need for a method to immobilize lead within perovskite solar cells to prevent its release into the environment.General Description

[0018] Perovskite solar cells have shown great promise for next-generation photovoltaic technologies due to their high efficiency and low fabrication costs. However, their long-term stability, especially against moisture and thermal degradation, remains a major challenge. One critical concern is the leakage of lead compounds upon exposure to water, which poses environmental and safety risks.

[0019] Efforts to mitigate this issue have included encapsulation and use of stabilizing materials. The present invention introduces a novel strategy to immobilize soluble lead compounds using hydrophilic polymers combined with functional additives.

[0020] The present disclosure relates to a lead-based perovskite solar cell comprising an additive that is a salt of the MaAnb type, where M and An stand for a cation and anion, respectively, a and b are appropriate stoichiometric subscripts. The present disclosure relates to an additive for immobilizing soluble lead compounds in perovskite solar cells.

[0021] The additive reacts with perovskite lead ions in the presence of water to form compounds with lower solubility and improved thermal stability compared to lead halides. Preferably, the hydrophilic polymer may be functionalized with lead-affinity groups such as sulfonate, phosphate, or carboxylate moieties to further enhance lead immobilization and containment.

[0022] The present disclosure is relevant in cases of cell breakage or fire by introducing specific additives within the cells.

[0023] The present disclosure relates to a process for immobilizing soluble lead compounds in perovskite solar cells by introducing additives that interact with lead-based components via ionexchange reactions, forming less soluble compounds with higher thermal stability. Additionally, a hydrophilic polymer is used to absorb water, expanding inside the cell to block water pathways through cracks, further reducing lead leakage.

[0024] Two approaches are disclosed: a) the addition of a substance to the cell, which reacts with soluble lead halides converting them into lead compounds with extremally low solubility in water and higher decomposition temperatures and; b) the addition of an element which blocks the humidity pathways through the defects in a damaged cell. These two pathways can be used either together or alone.

[0025] The present disclosure relates to a perovskite solar cell comprising an additive, wherein said additive is a MaAnb salt type, wherein M and An are independentely selected, M is a cation; An is an anion, a and b are appropriate stoichiometric subscripts.

[0026] In one embodiment, the salt is selected from MH2PO4, M2HPO4, M3PO4, MHCO3, M2CO3, MHSO4, M2SO4, MHS, M2S, MHC2O4, M2C2O4, M2MOO4, M2(MoO4*nMoO3), MHW04, M2W2O7, and M is the cation of an alkaline metal, ammonium, ammonium ion derivatives or any other singly charged cation. In another embodiment, the salt is selected from Mfl-^PCUh, MHPO4, M3(PO4)2, M(HCO3)2, MCO3, M(HSO4)2, MSO4, M(HS)2, MS, M(HC2O4)2, MC2O4, MMOO4, M(MoO4*nMoO3), MfHWCUh, MW2O7, wherein M is selected from Ca2+; Mg2+; Sr2+Ba2+; Cu2+Fe2+; Ni2+; Mn2+; Zn2+; Cr2+; Sn2+; VO2+; TiO2+; N2H62+; Al3+, Sc3+, Y3+, Au3+.

[0027] In one embodiment, An in the perovskite solar cell is selected from a list consisting of: H2PO4’, HPO42’, PO43’, HCO3’, CO32’, HSO4’, SO42’, HS; S2’, HC2O4’, C2O42’, MoO42’, (MoO4*nMoO3)2’ , MHWO4, M2W2O7, and M is the cation of an alkaline metal, ammonium, ammonium ion derivatives.

[0028] In one embodiment, the additive salt in the perovskite solar cell is selected from M(H2PO4)2, MHPO4, M3(PO4)2, M(HCO3)2, MCO3, M(HSO4)2, MSO4, M(HS)2, MS, M(HC2O4)2, MC2O4, MMOO4, M(MoO4*nMoO3), M(HWO4)2.

[0029] In one embodiment, the additive is used in the dry dehydrated form / compound.

[0030] In another embodiment, the additive is used as a dried hydrated compound.

[0031] In one embodiment, the perovskite solar cell is a multi-layer device.

[0032] In another embodiment, the additive salt used in the perovskite solar cell is a salt mixture or mixed salts.

[0033] In one embodiment, the perovskite solar cell comprises a glass substrate, a perovskite photovoltaic layer over said glass substrate directly or through an intermediate layer.

[0034] In one embodiment, a in the formulation of the additive used in the perovskite solar cell is the number of moles of M and 0 < a < 4.

[0035] In one embodiment, b in the formulation of the additive used in the perovskite solar cell is the number of moles of An and 0 < b < 3.

[0036] In one embodiment, the amounts of the additive in the perovskite solar cell are at least 0.14 pmol / cm2in the case of a single charged anion in the salt; at least 0.07 pmol / cm2in the case of a double-charged anion and at least 0.05 pmol / cm2in the case of a three-charged anion.

[0037] In one embodiment, the additive is loaded into a hydrophilic polymeric material that expands when in contact with water.

[0038] In another embodiment, the hydrophilic polymeric material is selected from polyethylene glycol), polyvinyl pyrrolidone, polyvinyl alcohol, polyacrylic acid, polyacrylamides, N-(2-hydroxypropyl) methacrylamide, divinyl ether-Maleic anhydride, polyoxazoline, polyphosphonate, polyphosphazene, xanthan gum, pectin, chitosan, dextran, carrageenan, guar gum, cellulose ethers, hyaluronic acid, albumin, starch as well as their derivates and mixtures thereof.

[0039] In one embodiment, the chemical amount of the additive loaded in the hydrophilic polymeric material is at least 0.42 pmol / cm2in the case of a single charged anion in the salt; at least 0.21 pmol / cm2in the case of a double-charged anion and at least 0.15 pmol / cm2in the case of a three-charged anion.

[0040] In an embodiment, the additive loading in the perovskite solar cell is defined based on the charge of the anion present in the MaAnb-type salt. Specifically, the minimum required quantities are at least 0.14 pmol / cm2for salts containing a single-charged anion, 0.07 pmol / cm2for salts with a double-charged anion, and 0.05 pmol / cm2for salts containing a triple-charged anion. For better results, when the additive is incorporated into a hydrophilic polymeric material, these thresholds increase to at least 0.42 pmol / cm2, at least 0.21 pmol / cm2, and at least 0.15 pmol / cm2respectively, depending on the anion charge, to ensure sufficient interaction and stabilization.

[0041] In one embodiment, the hydrophilic polymeric material is functionalized with lead- affinity / anchoring groups such as sulfonate-, phosphate-, carboxylate-functionalized polymers.

[0042] In one embodiment when in contact with water, the anion of the salt forms a product with the lead cations of the perovskite solar cell that have lower solubility in water than the lead halide constituting the perovskite solar cell.

[0043] In yet another embodiment, the additive is placed on the glass cover of the perovskite solar cell.

[0044] In one embodiment, the additive is placed on top of the perovskite photovoltaic layer.

[0045] In another embodiment, the additive is placed inside the perovskite solar cell in the form of a free-standing layer.

[0046] In yet another embodiment, the additive is deposited on the same substrate as the perovskite photovoltaic layer, directly or through an intermediate layer on the glass substrate, alternating either randomly or periodically on the substrate with the perovskite photovoltaic layer.

[0047] The present disclosure also relates to the use of a salt of the MaAnb type in the immobilization of lead compounds in perovskite solar cell.

[0048] The present disclosure also relates to the use of a salt of the MaAnb type as an immobilizer of lead compounds, preferably as an immobilizer of lead compounds in perovskite solar cells as a higher thermal stability improver.

[0049] The present disclosure also relates to the use of a salt of the MaAnb type as a higher thermal stability improver in a perovskite solar cells.

[0050] The present disclosure relates to a lead-based perovskite solar cell with an additive for lead immobilization in case the cell breaks, loses its hermicity or in the case of fire.

[0051] The present disclosure also relates to a process for immobilizing soluble lead compounds in perovskite solar cells. This process involves introducing specific additives that, in the presence of water, form less soluble and thermally stable lead compounds through ion-exchange reactions. Additionally, the use of a hydrophilic polymer as a water absorber further reduces lead release by blocking water pathways through cracks in the cell. Experimental results show significant reductions in lead ion release, enhancing the safety and environmental compatibility of perovskite solar cells.

[0052] An additive is introduced in the perovskite solar cell which, in the presence of water, reacts with the soluble lead compounds of the cell, forming less soluble lead compounds; this disclosure also discloses that the additive can be immobilized in an additive that expands under exposure to water, blocking the water path through defects in the package. The disclosed perovskite solar cell with the additive for lead immobilization aims at preventing water-soluble lead-based compounds to leak from the cell into the environment.

[0053] An aspect of this disclosure is described as an additional additive to the perovskite solar cells for the immobilization of soluble lead compounds inside the perovskite solar cells by converting them into less soluble compounds.

[0054] In this disclosure, said additive is a salt that in the presence of water chemically interacts via an ion-exchange reaction with soluble lead halides, present in a lead-based perovskite solar cell, forming lead compounds with lower solubility in water than the corresponding lead halide(s).

[0055] Said insoluble lead compounds, or lead compounds with very low solubility in water, produced by an ion-exchange reaction also display higher melting and boiling temperatures than the initial lead halide.

[0056] To obtain the better results the said additive, namely the salt, can be loaded in a waterabsorbing additive material, which in the presence of water releases the salt allowing it to react with the lead halides of the perovskite solar cell.

[0057] Said water-absorbing material is a dried hydrophilic polymeric material which expands physically when in contact with water, occupying the free internal volume of the perovskite solarcell, blocking the pathways for water and soluble lead species in the damaged cell. The material expands and can fill and close fractures in the perovskite solar cell.

[0058] Said hydrophilic polymeric material loaded with said salts is introduced in the perovskite solar cell package such as it occupies the free volume in the cell.

[0059] Said hydrophilic polymeric material loaded with said salts contacts with the active layers of the perovskite solar cell or is a constituting part of the perovskite solar cell.

[0060] In this disclosure, said hydrophilic polymeric material loaded with said salts can be applied over the perovskite solar cell active layers forming a layer, which after closing the perovskite solar cell package flows to occupy free volume of the cell.

[0061] Said hydrophilic polymeric material loaded with said salts can be placed inside the perovskite solar cell package in the form of a free-standing layer.

[0062] Said hydrophilic polymeric material loaded with said salts can be introduced in the perovskite solar cell package as an island-like layer, powder layer or a combination thereof.

[0063] Said water-absorbing hydrophilic polymeric material can be made of a hydrophilic water- extendable polymer loaded with a single or a mixture of salts, organic or inorganic, capable of ion exchange or complexation reactions with the lead components of the perovskite solar cell to form insoluble lead compounds or lead compounds with very low solubility in water.Brief description of drawings

[0064] For easier understanding of this disclosure, figures are attached to represent the preferred forms of implementation which nevertheless are not intended to limit the technique disclosed herein.

[0065] Figure 1 illustrates a top view of a perovskite solar cell (100) with the additive (101) for the immobilization of water-soluble lead compounds. The perovskite solar cell includes components of the perovskite photovoltaic layer (102) placed on the glass substrate (103), the cover of the cell (104) and sealing material (105).

[0066] Figure 2 shows cross-sectional side views of the perovskite solar cell (100) represented in Figure 1 taken along the line 1-1 in Figure 1 and illustrates non-limiting examples of the positioning of the additive (101) inside the perovskite solar cell (100) with respect to theperovskite photovoltaic layer (102), glass substrate (103), cover of the cell (104) and sealing material (105).Wherein:In the embodiment (2A) the additive (101) is applied on the cover of the cell (104) of the perovskite solar cell (100), opposite to that where the perovskite photovoltaic layers (102) are applied;

[0067] In the embodiment (2B) the additive (101) is attached to the perovskite photovoltaic layer(102).

[0068] In the embodiment (2C) the additive (101) is applied inside encapsulated perovskite solar cell (100) in the form of a free-standing film.

[0069] In the embodiment (2D) the additive (101) is applied on the same glass substrate (103) as the perovskite photovoltaic layers (102) and alternating with them either randomly or periodically with the perovskite photovoltaic layer (102).

[0070] Figure 3 illustrates top views of the non-limiting examples for the placement of the additive (101) in the perovskite solar cell (100) whenever it is placed in a cell according to any of the embodiments (2A-2D) shown in Figure 2 or combination thereof.

[0071] Figure 4 illustrates a cross-sectional side view of a perovskite solar cell (100) comprising the disclosed additive (101) according to an embodiment hereof:(102) is the perovskite photovoltaic layer;(103) is the glass substrate;(104) is the cover glass;(105) is the sealing material.

[0072] As a non-limiting example, the perovskite photovoltaic layer (102) is constituted by compact titanium dioxide blocking layer (106); titanium dioxide mesoporous layer infiltrated with CHsNHsPbls (107); zirconia oxide porous layer (108); a porous carbon layer (109) and (110) represents an artificial defect in the cell.Detailed description

[0073] The present disclosure relates to a process for the immobilization of soluble lead compounds in perovskite solar cells, particularly in the event of cell breakage or fire, by introducing specific additives into the cell structure. These additives, upon contact with water,undergo an ion-exchange reaction with the lead-based components of the perovskite layer, resulting in the formation of less soluble compounds with significantly higher thermal stability. Remarkably, the lead ion release from perovskite cells treated with the disclosed additives is reduced by two orders of magnitude compared to untreated cells under leakage conditions.

[0074] In a further aspect, the disclosure describes the incorporation of a water-absorbing material within the cell, based on a hydrophilic polymer matrix. This material rapidly absorbs and swells in the presence of water, expanding inside the cell and effectively blocking the ingress of water through cracks or fractures. In this configuration, the release of lead from the perovskite solar cell is reduced by up to four orders of magnitude compared to a blank (untreated) device, demonstrating a substantial improvement in safety and environmental protection.

[0075] Now, preferred embodiments of the present disclosure is described in detail concerning the annexed drawings. The described embodiments are not intended to limit the scope of this disclosure.

[0076] The present disclosure describes an additional additive (Figure 1, (101)) to lead-based perovskite solar cells (100) for reducing lead leakage from the cells into the environment, and the immobilization of soluble lead species in the perovskite solar cells by converting them into insoluble lead compounds orto lead compounds with low solubility in water, with higher melting, boiling and decomposition temperatures.

[0077] In one embodiment, the additional additive is a salt, which in the presence of water, chemically interacts via an ion exchange reaction with the soluble lead halides present in a perovskite solar cell. Said ion-exchange reactions result in the formation of insoluble lead compounds or lead compounds with lower water solubility than the initial lead-based components of the perovskite solar cell, thus reducing lead escape from the cell to the environment.

[0078] Said salts are noted herein and after as MaAnb, where M and An stand for a cation and anion, respectively; a and b are appropriate stoichiometric subscripts.

[0079] It is disclosed that a non-limiting criterion for the selection of said salts for the ion exchange reaction is the ability of the anionic part of it to form a product with lead cations interact with additive and form which have a lower solubility products in water than the lead halide constituting the perovskite light absorber in the photovoltaic cell.

[0080] Said insoluble lead products or lead products with low solubility in water are noted herein and after as PbyAnz, where y and z are stoichiometric subscripts.

[0081] Said ion-exchange reaction, induced by the water with the added salt additive (101), is expressed in the general not limiting way as follows:

[0082] In an embodiment, the lead compound formed in said ion exchange reaction (eq.2) has a higherthermal decomposition temperature than the lead halide constituting the perovskite layer in the perovskite solar cell.

[0083] The efficacy of the salt additive (101) in decreasing the lead ions release from a damaged perovskite solar cell (100) into the environment, when said salts are loaded into this additive (101), can be estimated as a certain coefficient (Ceff). This coefficient is equal to the ratio of the equilibrium concentration of lead ions [Pb2+] in a saturated solution of lead halide (PbX2) of the perovskite to the equilibrium concentration of lead ions in a saturated solution of PbyAnzformed in said ion-exchange reaction: which is equal to:where Ksp(PbX2) and Ksp(PbyAnz) are the solubility product constants of PbX2and PbyAnzrespectively.

[0084] Alternatively:

[0085] where S(PbX2) and S(PbyAnz) are the solubilities of the respective lead compounds in mass units per volume; M(PbX2) and M(PbyAnz) are the molar masses of the lead salts.

[0086] Non-limiting examples of the salts MaAnb are: MH2PO4, M2HPO4, M3PO4, MHCO3, M2CO3, MHSO4, M2SO4, MHS, M2S, MHC2O4, M2C2O4, M2MOO4, M2(MoO4*nMoO3), MHWO4, M2W2O7wherein M, in the most acceptable but not limiting case, is the cation of an alkaline metal (Li+, K+, Na+, Rb+, Cs+), ammonium (NH4+), ammonium ion derivatives or any other singly charged cation.

[0087] In an embodiment, the salts of the doubly charged cation M, as non-limiting examples Ca2+; Mg2+; Sr2+Ba2+; Cu2+Fe2+; Ni2+; Mn2+; Zn2+; Cr2+; Sn2+; VO2+; TiO2+; N2H62+or triply charged cation, like Al3+are used whenever they are soluble in water and meet the criteria.

[0088] In an embodiment, the salts of the doubly charged cation M, as non-limiting examples M(H2PO4)2, MHPO4, M3(PO4)2, M(HCO3)2, MCO3, M(HSO4)2, MSO4, M(HS)2, MS, M(HC2O4)2, MC2O4, MMOO4, M(MoO4*nMoO3), M(HWO4)2, MW2O7wherein M is Ca2+; Mg2+; Sr2+Ba2+; Cu2+Fe2+; Ni2+; Mn2+; Zn2+; Cr2+; Sn2+; VO2+; TiO2+; N2He2+are used whenever they are soluble in water and meet the criteria.

[0089] The triply charged cations are selected from Al3+, Sc3+, Y3+, Au3+.

[0090] In an embodiment, said salt additives used in dry dehydrated form. In another embodiment, the salt additive is used as a dried hydrated compound.

[0091] In an embodiment, any other compound that meets the criteria non-limiting and / or has a higher thermal decomposition temperature than the lead halide constituting the perovskite light absorber might be used as the additional additive (101) for lead immobilization in the perovskite solar cell.

[0092] Table 1 lists the coefficients Ceff calculated from the solubility data of some non-limiting examples of PbyAnzcompounds and PbX2constituting the perovskite light-absorbing material.Table 1. Coefficients Ceff calculated using (eq.5) and solubilities of the corresponding compounds at 20-C.

[0093] It is disclosed the minimum amount (ns) of salt placed in the perovskite solar cell for the efficient conversion of the soluble lead of the perovskite layer into insoluble or low water-soluble compounds. The amount ns, in moles, should be double the amount of the perovskite lightabsorbing material (np) if the said salt includes a single-charged anion (An (eq.6); nsshould beequal to npif a double-charged anion (An2salt or its protonated form (HAn j is used (eq. 7,8); ns should be 2 / 3 of the npif the salt contains a three-charged anion (An3or any of its protonated forms (eq. 9-10):Pb2++ 2An_<=> PbAn2(eq.6)Pb2++ An2-<=> PbAn (eq.7)Pb2++ HAn" <=> PbAn + H+(eq.8)Pb2++ 2 / 3An3’ « l / 3Pb3An2(eq.9)Pb2++ 2 / 3HAn2’ « l / 3Pb3An2+ H+(eq.10)Pb2++ 2 / 3H2An" « l / 3Pb3An2+ 2H+(eq.11)

[0094] The content of water-soluble forms of lead in a conventional perovskite solar cell is approximately 0.07-0.14 micromoles per cm2.

[0095] The following minimum amounts of the salt additive (101) should be added to a perovskite solar cell for effective binding of lead (micromole per cm2of the perovskite layer): at least 0.14 in the case of a single charged anion in the salt; at least 0.07in the case of a doublecharged anion and at least 0.05 in the case of a three-charged anion.

[0096] In one embodiment, the additive is loaded into a water-absorbing material. The waterabsorbing material is a hydrophilic polymeric material which expands physically when in contact with water, occupying free internal volume of the perovskite solar cell, blocking the pathways for water and soluble lead species in the damaged cell, as shown in Figure 1, 2 and 3.

[0097] Said hydrophilic polymeric material loaded with said salts is introduced in the perovskite solar cell such as it occupies free volume. The amount of the added polymer varies from 4.3 to 90.7 mg per cm2of the cell area.Said hydrophilic polymeric material loaded with said salts contacts with the active perovskite solar cell layers or is a constituting part of the perovskite solar cell.

[0098] In one embodiment, the chemical amount of the salt additive (101) loaded in the hydrophilic polymeric material should be three to thirty times higher than the said minimum amount required to fulfill reaction (eq.2), that is in micromole per cm2of the perovskite layer: at least 0.42 pmol / cm2in the case of a single charged anion in the salt; at least 0.21 pmol / cm2in the case of a double-charged anion and at least 0.15 pmol / cm2in the case of a three-charged anion.

[0099] Upon swelling and expanding, said hydrophilic polymeric material releases the loaded salts, allowing them to react with the lead halides from the perovskite layer of the perovskite solar cell, forming insoluble or lead compounds with low water solubility according to eq. (2).

[0100] Said hydrophilic polymeric material is synthetic or natural by origin.

[0101] As non-limiting examples of said hydrophilic polymeric materials are selected from polyethylene glycol), polyvinyl pyrrolidone, polyvinyl alcohol, polyacrylic acid, polyacrylamides, N-(2-hydroxypropyl) methacrylamide, divinyl ether-Maleic anhydride, polyoxazoline, polyphosphonate, polyphosphazene, xanthan gum, pectin, chitosan, dextran, carrageenan, guar gum, cellulose ethers, hyaluronic acid, albumin, starch as well as their derivates and mixtures thereof.

[0102] In another embodiment, said hydrophilic polymeric material is functionalized with lead- affinity / anchoring groups such as sulfonate-, phosphate-, carboxylate-functionalized polymers are preferably used among the others.

[0103] In another embodiment, the optimum mass fraction of the additive in said hydrophilic polymeric material varies from 0.5 to 30 wt.%.

[0104] In one embodiment, another aspect of the disclosure is the position of the additive (101) in the perovskite solar cell (100) with respect to the perovskite photovoltaic layer (102), glass substrate (103), cover of the cell (104) and sealing material (105).

[0105] In an embodiment, the additive (101) is placed on the glass cover (104) of the perovskite solar cell (100) with the gap between the perovskite photovoltaic layer arrangement (102) - Figure 2A.

[0106] In an embodiment, said additive (101) is placed on top of the perovskite photovoltaic layer arrangement (102) with the gap between the cover of the cell (104) - Figure 2B.

[0107] In an embodiment, said additive (101) is applied as a free-standing film inside the perovskite solar cell (100) - Figure 2C.

[0108] In an embodiment, said additive (101) is deposited on the same substrate as the perovskite photovoltaic layer (102), directly or through an intermediate layer on the glass substrate (103), alternating either randomly or periodically on the substrate with the perovskite photovoltaic layer (102) - Figure 2D.

[0109] In an embodiment, the additive (101) is placed uniformly opposite the perovskite photovoltaic layer (102) either on the cover of the cell (104) or on top of the perovskite photovoltaic layers (102) - Figure 3A.

[0110] In an embodiment, the additive (101) is placed around the perimeter of the perovskite photovoltaic layer (102) - Figure 3B.

[0111] In an embodiment, the additive (101) is placed in the cell in an arbitrary or in deterministic way to form a patterning coating - Figure 3A and Figure 3B.

[0112] In one embodiment, the additive (101) loaded into the hydrophilic polymeric material is positioned in the same manner as described in the previous embodiments.Example 1.

[0113] A perovskite solar cell (100) with the additive (101) was made from one of the following salts - K2CO3, K2SO4, Na2HPO4or NaH2PO4.

[0114] This example shows a possible configuration of the perovskite solar cell (100) with the additive (101), placed on the cover of the cell (104) of the perovskite solar cell (100), opposite to the perovskite photovoltaic layer (102), according to the scheme shown in Figures 2A and 3A.

[0115] To form the perovskite solar cell (100) several components were stacked over a conductive substrate (103), which was made of transparent conducting oxides (TCO); the components forming the perovskite photovoltaic layer (102) were a compact titanium dioxide blocking layer (106), a titanium dioxide mesoporous layer (107), a zirconia oxide porous layer (108), and a porous carbon layer (109), as shown in Figure 4. The geometrical area of the perovskite light absorber layer (102) in the cells was 4 cm2. The perovskite light absorber was CHsNHsPbh. The components were enclosed by a sealing material (105) made from glass frit. The conductive substrate was sandwiched with a second glass substrate (104) with the additive (101) by melting the glass frit sealing material with a laser source. Before sandwiching, the salt - either Na2CC>3 or Na2SO4or Na2HPO4or NaFhPC , was uniformly deposited on the cover glass (104) by spray-pyrolysis; a 0.1 M aqueous solution of the salt was sprayed on a preheated (140^C) glass cover (104). The amount of the sprayed salts, determined from the increase of the glass cover (103) mass after spraying, was 0.6, 0.7, 0.8 and 0.7 pmol / cm2of K2CO3, K2SO4, Na2HPO4and NaFhPC , respectively. Both substrates were sealed by heating the glass frit sealing material (105) to the sealing temperature using an infra-red (IR) laser source; a completely encapsulatedpackaging was formed. A through-hole (110) of 1 mm in diameter was drilled in the cover glass to simulate the damage of the perovskite solar cell (100). The cell was entirely dipped for 24 h in 20 ml of deionized water. The amount of lead released from the perovskite solar cell (100) was determined from the concentration of lead in the water, which was obtained by inductively coupled plasma emission spectroscopy. The amount of lead released from the perovskite solar cell (100) without the additive (101) was used as a control sample.

[0116] In example 1 the determined concentrations of lead in the water after cell immersion are listed in Table 2.The efficacy of reducing the realize of soluble lead was calculated as a ratio of lead ion concentration in the control sample to the lead ion concentration in the sample with the additive (101) and is given in Table 2 as well.

[0117] Table 2 of Example 1 - Lead release from the perovskite solar cell with the additive (101), with salt comprising the additive (101), the detected concentration of lead ions in ppm and the efficacy of reducing lead ion release (Ceff).Example 2

[0118] A perovskite solar cell (100) with the salt additive (101) loaded in a hydrophilic waterexpandable polymer film.

[0119] In example 2, the glass substrate (103), cover of the cell (104), sealing material (105), and the sequence of steps for preparing the perovskite photovoltaic layer (102), cell sealing, as well as a drilled hole in the cell (110) for simulating the hermicity failure, are the same as in example 1.

[0120] The additive (101) was applied in the cell in the form of a free-standing film made from Polyvinyl Alcohol (PVA) and of Hydroxypropyl Cellulose (HPC) with K2CO3 or K2SO4 or Na2HPO4 as added salt additive (101). The said polymeric films loaded with the salts were obtained by drying in the vacuum oven at 50^C, the homogenized solutions comprised 0.1-0.6 g of the salt (respectively K2CO3, K2SO4, Na2HPO4), 0.1-0.25 g of Hydropropyl Cellulose, 0.7-2 g of Polyvinyl alcohol, 0.4-1.8 ml of Poly ethylene glycol and 10 ml of deionized water.

[0121] Said polymeric films were then placed inside the perovskite solar cell (100), between the glass substrate (103) and the perovskite photovoltaic layers (102), and the cover of the cell (104) according to the scheme of the method shown in Figure 2C; the perovskite solar cell (100) was then sealed as described in example 1 and dipped into 20 ml of the deionized water for 24 h.

[0122] In example 2 the determined concentrations of lead in the water after the perovskite solar cell immersion are listed in Table 3. The efficacy of reducing lead realize (Ceff) are given in the Table 3 as well.

[0123] Table 3 of example 2 - Lead release from the perovskite solar cell with the additive (101) loaded in a hydrophilic polymer.

[0124] Where ranges are given, endpoints are included. Furthermore, it is to be understood that unless otherwise indicated or otherwise evident from the context and / or the understanding of one of ordinary skill in the art, values that are expressed as ranges can assume any specific value within the stated ranges in different embodiments of the invention, to the tenth of the unit of the lower limit of the range, unless the context clearly dictates otherwise. It is also to be understood that unless otherwise indicated or otherwise evident from the context and / or the understanding of one of ordinary skill in the art, values expressed as ranges can assume any subrange within the given range, wherein the endpoints of the subrange are expressed to thesame degree of accuracy as the tenth of the unit of the lower limit of the range. Notwithstanding the above, where a range is defined in the form "0 < X < Y", the lower limit of zero (0) is explicitly excluded from the scope of the range. This exclusion applies to both the main range and any derived subranges.

[0125] The term "comprising" whenever used in this document is intended to indicate the presence of stated features, integers, steps, components, but not to preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0126] The disclosure should not be seen in any way restricted to the embodiments described and a person with ordinary skill in the art will foresee many possibilities to modifications thereof.

[0127] The above-described embodiments are combinable.

[0128] The following claims further set out particular embodiments of the disclosure.

[0129] The following references should be considered herewith incorporated in their entirety:[1] Green, M. A. et al. (2023). Solar cell efficiency tables (version 53). Progress in Photovoltaics: Research and Applications, 32(1), 3-13. doi:10.1002 / pip.3750[2] US09231136B2 - Wu Chun-Guey, Chiang Chien-Hung, Method For Preparing Perovskite Film And Solar Cell Thereof[3] Ahmed, Sultan, et al.2024. "Recent Trends and Challenges in Lead-Free Perovskite Solar Cells: A Critical Review." Appl. Energy Mater., 7(4):1382. 10.1021 / acsaem.3c02327

Claims

CLAIMS1. Perovskite solar cell comprising an hydrophilic polymeric material and an additive, wherein said additive is a MaAnb salt type, wherein M and An are independentely selected,M is a cation;An is an anion, a and b are appropriate stoichiometric subscripts; wherein the additive is incorporated into the hydrophilic polymeric material, and wherein the loaded hydrophilic polymeric material expands upon contact with water.

2. Perovskite solar cell according to the previous claim, wherein An is selected from a list consisting of: H2PO4", HPO42’, PO43’, HCO3", CO32’, HSO4", SO42’, HS", S2’, HC2O4", C2O42’ , MOO42-, (MoO4*nMoO3)2-, MHWO4, M2W2O2, and M is the cation of an alkaline metal, ammonium, ammonium ion derivatives.

3. Perovskite solar cell according to any of the previous claims, wherein M is selected from a list consisting of: Li+,Na+, K+,Rb+, Cs+, NH4+, Ca2+, Mg2+; Sr2+, Ba2+, Cu2+, Fe2+, Ni2+, Mn2+,Zn2+, Cr2+, Sn2+, VO2+, TiO2+; N2H62+, Al3+, Sc3+, Y3+, Au3+.

4. Perovskite solar cell according to any of the previous claims, wherein a is the number of moles of M and ranges from 0 < a < 4; preferably preferably 1< a < 2..

5. Perovskite solar cell according to any of the previous claims, wherein b is the number of moles of An and ranges from 0 < b < 3; preferably 1< b < 2.

6. Perovskite solar cell according to any of the previous claims, wherein the additive salt is selected from M(H2PO4)2, MHPO4, M3(PO4)2, M(HCO3)2, MCO3, M(HSO4)2, MSO4, M(HS)2, MS, M(HC2O4)2, MC2O4, MMOO4, M(MoO4*nMoO3), M(HWO4)2.

7. Perovskite solar cell according to any of the previous claims, wherein the additive salt is a salt mixture or mixed salts.

8. Perovskite solar cell according to any of the previous claims, wherein the additive is in a dry dehydrated form / compound.

9. Perovskite solar cell according to any of the previous claims, comprising a glass substrate, a perovskite photovoltaic layer over said glass substrate directly or through an intermediate layer.

10. Perovskite solar cell according to any of the previous claims, wherein the glass substrate and / or the perovskite photovoltaic layer comprises the additive.

11. Perovskite solar cell according to any of the previous claims 1-7, 9-10, wherein the additive is used as a dried hydrated compound.

12. Perovskite solar cell according to any of the previous claims, wherein the amounts of the additive in said perovskite solar cell are at least 0.14 pmol / cm2in the case of a single charged anion in the salt; at least 0.07 pmol / cm2in the case of a doublecharged anion and at least 0.05 pmol / cm2in the case of a three-charged anion.

13. Perovskite solar cell according to any of the previous claims, wherein, upon exposure to water, the anion of the salt interacts with lead cations present in the perovskite solar cell to form a less soluble product.

14. Perovskite solar cell according to any of the previous claims, wherein the lead cations react with the additive to generate compounds exhibiting lower aqueous solubility than the lead halide present in the perovskite solar cell.

15. Perovskite solar cell according to any of the previous claims, wherein the hydrophilic polymeric material is selected from poly(ethylene glycol), polyvinyl pyrrolidone, polyvinyl alcohol, polyacrylic acid, polyacrylamides, N-(2-hydroxypropyl) methacrylamide, divinyl ether-Maleic anhydride, polyoxazoline, polyphosphonate,polyphosphazene, xanthan gum, pectin, chitosan, dextran, carrageenan, guar gum, cellulose ethers, hyaluronic acid, albumin, starch or mixtures thereof.

16. Perovskite solar cell according to any of the previous claims, wherein the amount of the additive in the hydrophilic polymeric material is at least 0.15 pmol / cm2.

17. Perovskite solar cell according to the previous claim, wherein the amount of the additive in the hydrophilic polymeric material is at least 0.42 pmol / cm2for a single charged anion in the salt; at least 0.21 pmol / cm2for a double-charged anion in the salt; at least 0.15 pmol / cm2for a three-charged anion in the salt.

18. Perovskite solar cell according to any of the previous claims 1-15, wherein the hydrophilic polymeric material is functionalized with lead-affinity / anchoring groups, wherein the lead-affinity / anchoring groups are selected from a list consisting of sulfonate-functionalized polymers, phosphate-functionalized polymers, carboxylate- functionalized polymers.

19. Perovskite solar cell according to any of the previous claims, further comprising a glass cover, wherein the glass cover comprises the additive.

20. Perovskite solar cell according to any of the previous claims, wherein the hydrophilic polymeric material loaded with the additive is placed on top of the perovskite photovoltaic layer.

21. Perovskite solar cell according to any of the previous claims, wherein the hydrophilic polymeric material loaded with the additive is placed inside said perovskite solar cell in the form of a free-standing layer.

22. Perovskite solar cell according to any of the previous claims, wherein the hydrophilic polymeric material loaded with the additive is deposited on the same substrate as the perovskite photovoltaic layer, directly or through an intermediate layer on the glass substrate, alternating either randomly or periodically on the substrate with the perovskite photovoltaic layer.

23. A process for obtaining a perovskite solar cell immobilizing soluble lead compounds in a perovskite solar cell, comprising: introducing additives described in any of the previous claims into the perovskite solar cell; allowing the additives to interact with lead-based components via an ion-exchange reaction in the presence of water, forming less soluble compounds with higher thermal stability.

24. Use of a salt of the MaAnb type as an imobilizer of lead compounds in perovskite solar cells as described in any of the claims 1-22.

25. Use of a salt of the MaAnb type as an imobilizer of lead compounds, preferably as an imobilizer of lead compounds in perovskite solar cells as a higher thermal stability improver.

26. Use of a salt of the MaAnb type as a higher thermal stability improver in a perovskite solar cells.

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